What is the conventional wisdom about treating a female guppy with testosterone?"

Harro Hieronimus, author of the Barron's book on Livebearers responded that the chances were that after the test the colors would fade, "...but she got a gonopodium and was a fade giant, nearly (a) male guppy."

If Harro was against the idea, Bill Allen, editor of the ALA publication Livebearers, was a little more encouraging and noted, "If done carefully, the female will show color temporarily and will not be sterilized. For more details, dosages, etc., refer to the ALA's
"Livebearers; Special Publication #4; Guppies", pp 46 to 54.

Another interesting topic discussed is using estrogen to ENHANCE fertility - the example cited is in albino strains which tend not to be prolific. Only available through the ALA, and a real bargain at $4 ($3.50 for 2 or more)."

I (should have but) didn't realize that there was a guppy issue in the ALA special publication series. They have seven special issues which collect many articles on a general topic published over the years in Livebearers.

Angelee was also wondering about her tap water and estrogen. Bill's comment about enhancing fertility with estrogen is interesting. Maybe "it is the water" as parents have kidded over the years!

When we were house hunting with an eye on finally getting out of grad school and settling down to start a family, we noticed a delightful, reasonably priced housing development near woodlands and forest preserves. Then I noticed a locally infamous chemical plant over the tree tops. They had made an agricultural fertilizer which had an estrogen like component. Male employees of that plant began to have all sorts of problems and charged mastectomies to the company.

The plant folded. We bought a lesser house miles to the west (and up wind.)

After Angelee's initial post I had jotted a preliminary NOTEPAD response to the Methyl testosterone question:

Many serious breeders wouldn't treat a female, but would have pretty detailed records of who has produced what in that strain (a studbook of sorts or a breeding registry). Even then one can't be 100% sure what will be produced.

According to the Gospel of Shubel ;)  (p. 134) a couple of his blue deltatail lines still throw occasional purples or greens along with the blues. He even suggests that breeding that male back to one of his sisters with the appropriate cast to her tail can produce some pretty decent green or purple fish. So he too is playing the (pretty favorable) odds with his blues. (Evidentally not singing them anyway.)

So hormone treating female guppies is not necessarilly the same as choking the golden goose. But I wouldn't really want to make her my chief breeder again.

... (I was really hoping that someone who had done that would respond to Guppylog.) If the speculations/suggestions below are wrong - in the experience of someone on this list or an acquaintance you have closely questioned - please correct me....

It is curious how much the guppy books don't address this issue. Taboo?

If a person had several females which looked like "peas in a pod", they could take a female which they were not likely to breed (let's assume they have a dozen females in a generation of that line). Would they breed and save the fry of more a couple of batches of one or two or maybe three females? So test number 8. :)

In this case it might make sense because that is not the fish you are likely to breed so who cares?

However many of us have guppies from shops or recent purchases at fish club events. We are unsure of what our fish will produce. If a specifically colored female has mated with males of radically different colors, her colors may not give a very accurate picture of what her fry will look like anyway. Look at gupppies' description of black x yellow guppies and what they will produce - if the lines are pure.

If you have one female guppy you really like and she has only been with a certain male, you may be able to guess from them what many of their offspring will be like. Dorsal and tail fins and maybe even some body color may suffice.

If you are still dying to determine what colors she carries, why don't you let her drop a good batch first so if she is damaged by the process later on, some fry remain?

I too would really like to know what some fish will produce. Sometimes a scientific curiosity may demand that. (A scientific curiosity might also demand dissection in some cases of illness.)